CVE-2026-21806: HCL BigFix Service Management is affected by an Administrative Session Concurrency vulnerability

Routine

LOW 3.1DOWNGRADE

CVE-2026-21806 is a low-severity flaw (CVSS 3.1) affecting bigfix service management. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

HCL BigFix Service Management is affected by an Administrative Session Concurrency vulnerability. The application allows multiple simultaneous authenticated sessions for the same administrative account, which could enable an unauthorized attacker to predict or hijack valid session identifiers. Successful exploitation allows an attacker to compromise affected administrative sessions and execute actions with full privileged user permissions.

Why this priority

No elevated risk signals yet

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	3.1 (Low)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.2% (top 90%)
CISA exploited list	No
Weakness	CWE-557
Published	2026-09-18
Last modified	2026-10-14

Publisher (CNA): HCL Software · Vendor: hcltech

Last updated 2026-10-14 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-09-18 12:17 UTCPublished CVE record published
2026-10-14 17:36 UTCUpdated Record last modified

hcltech bigfix service management DOWNGRADE

Affected: 27

Fixed in: no fixed release known

Safe to downgrade to: a release before 27

1. Check installed version

apt-cache policy bigfix-service-management || rpm -q bigfix-service-management || bigfix-service-management --version

2. No fixed release: DOWNGRADE to a release before 27 (Debian / Ubuntu)

apt-cache madison bigfix-service-management sudo apt install bigfix-service-management=<VERSION_BEFORE_27> sudo apt-mark hold bigfix-service-management

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list bigfix-service-management sudo dnf downgrade bigfix-service-management-<VERSION_BEFORE_27> sudo dnf versionlock add bigfix-service-management

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-21806?

bigfix service management: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-21806 being exploited?

CVE-2026-21806 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-21806 affect?

CVE-2026-21806 affects bigfix service management. Severity is low (CVSS 3.1). HCL BigFix Service Management is affected by an Administrative Session Concurrency vulnerability. The application allows multiple simultaneous authenticated sessions for the same administrative account, which could enable an unauthorized at

How urgent is CVE-2026-21806?

Priority 13/100. No elevated risk signals yet.

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References

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